The invention disclosed herein relates generally to arrangements for pivotally mounting levers in lever operated mechanisms, and more particularly to a lever mounting arrangement for facilitating lever interchangeability in plunger actuated electrical switches.
Lever operated electrical switches are used in a wide variety of applications. The same electrical switch mechanism may be used in applications requiring a large number of different operating levers. Electrical switches of the same design may, in fact, be fitted with any of several hundred different operating levers depending on the requirements of the applications in which they are to be used. In order to avoid the need for maintaining a stock of complete switch/lever assemblies having all lever configurations, various designs are known to permit an appropriate operating lever to be installed in the field as the need for a switch with a particular lever configuration arises. It is also beneficial in many circumstances to be able to remove and/or interchange operating levers.
In general, the designs which are intended for installation of operating levers after manufacture of the switches fall into one of two categories. In one category, the lever or some portion thereof is resilient, thus permitting it to be snapped into place in or on some portion of the switch housing. In the other category, at least some portion of the switch housing is resilient, thus permitting pivot defining portions of the levers to be snapped past protrusions or into recesses in the switch housing.
The requirements presently placed on many switches are not well met by known switch designs in either of the above design categories. Some of the principal requirements include low cost, long life, low actuating force and actuating force which remains substantially constant throughout the operating life. Maximizing any one of these characteristics often involves comprises relating to one or more of the other characteristics. The maturation of technologies which permit very low force, long life electrical switching, such as Hall effect or other solid state switching where operating life capabilities and requirements may exceed 100,000,000 operating cycles, compound the problem of achieving a suitable mechanical actuator design. In designs in which the operating lever is required to bend during each operation, careful consideration must be given to stress and fatigue in the lever. To avoid stress and fatigue failures, it has been found desirable to utilize a pivoting rigid operating lever. Use of a rigid operating lever also facilitates comliance with vibration requirements and permits tight control over pivot axis location and lever positioning.
For purposes of reducing pivot point stress and wear which affect both operating life and consistency of operating force, it is necessary to have adequate bearing surface area. In known designs utilizing rigid levers and resilient plastic switch housings, bearing surface area is limited because the amount by which the housing can be deformed is small. Also, snapping the lever past projections in the housing can raise a burr which may adversely affect low force operation and/or operating life.
The geometry of the lever and plunger arrangement should also be such as to minimize side forces and sliding of the lever on the plunger. This requires that the pivot axis be located close as possible to the plane which is perpendicular to the direction of plunger movement at the point of contact between the lever and plunger.
Finally, with regard to lever interchangeability, prior designs are generally not intended for or suitable for removing or interchanging operating levers.
The applicant has provided a unique operator lever mounting arrangement with improved characteristics as to the noted requirements and desirable features by employing a rigid operator lever of simple configuration which is capable of simple, convenient and repetitive lever installation and removal.